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New P38 90" wing motor mount - 11/18/2012 2:46 AM   
Airshow



Posts: 25
Score: 100
Joined: 12/14/2008
Last Login: 1/20/2013
From: Pasadena, MD, USA
Status: offline 		I am building the plane now and have 2 maybe problems

1# the manual shows motor as a side mount and a lot of cutting of the cowl
but there is lots of room if you mount them upside down and less cutting is this a problem?
using 2 91=4s
2# will i have to reverse one of the motors counter clock wise one of the guys at the field said I would??
not sure?
I have a Twin Star and have no problem

Thanks and have a great day

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RE: New P38 90 - 11/18/2012 2:57 AM   
speedracerntrixie


 

Posts: 2383
Score: 189
Joined: 6/7/2010
Last Login: 5/24/2013
From: San Jose, CA, USA
Status: offline 		Running 4 cycle engines inverted should not be an issue just as long as the fuel tanks centerline is not higher then the carb center.  I have run 2 strokes inverted on a couple of occasions and hated the airplanes because of it. I have not flown many twins but I have virtually never seen one with counter rotating engines. The key I would think is make darned sure that both engines are running 100% reliable and have rerasonable close RPMs at all throttle settings.


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RE: New P38 90 - 11/19/2012 11:10 PM   
Granpooba


 

Posts: 328
Score: 110
Joined: 10/24/2002
Last Login: 5/6/2013
From: Queensbury, NY, USA
Status: offline
quote:

ORIGINAL: Airshow

I am building the plane now and have 2 maybe problems

1# the manual shows motor as a side mount and a lot of cutting of the cowl
but there is lots of room if you mount them upside down and less cutting is this a problem?
using 2 91=4s
2# will i have to reverse one of the motors counter clock wise one of the guys at the field said I would??
not sure?
I have a Twin Star and have no problem

Thanks and have a great day


No, you will not reverse one of the motors.

As previously stated, both engines running perfectly insync, will work. Friend of mine also had a Twin Star and flew great. Even had a couple of engine outs and brought in for good landings.

Not even all full size prop driven aircraft have counter rotating props.

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RE: New P38 90 - 11/25/2012 9:23 PM   
DGM


 

Posts: 83
Score: 100
Joined: 6/27/2005
Last Login: 5/24/2013
From: , NV, USA
Status: offline 		I am on my second 90" P- 38. Electric with both props turning the same way. No problems. I considered glow power but the tanks came out quite a bit below the carb, so decided on electric. Plane is eazy to fly and looks great in air. Nice thing about electric, other than dependability, is you can climb to altitude and shut down motors and glide around. Yes it does glide well. Then start up and continue powered flight.

Flew a B-26 with glow and that worked well too. Tune each engine individually so each engine is running at its best, full speed, idle and inbetween. DO NOT try to match RPMs. A few hundred RPM difference will not affect flight.

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RE: New P38 90 - 11/26/2012 1:20 AM   
kthmarks


 

Posts: 58
Score: 100
Joined: 3/11/2006
Last Login: 5/9/2013
From: , GA, USA
Status: offline 		This may be of a little help, below is a link to the mods I did on installing twin saito's (inverted) in a twin otter. Also, you might seriously consider installing a Twin Sync to help manage the engines and to ensure a margin of safety in the event you have an engine out. I installed one in the Otter and it has been a real pleasure to fly. Not to mention it saved my bacon once on a touch-n-go when I lost an engine.

http://www.rcuniverse.com/forum/fb.asp?m=11033547

Twin Sync
http://www.troybuiltmodels.com/items/WRCTWINSYNC.html

_____________________________

Keith Marks
AMA 49064

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